Set top boxes can be used to receive satellite, terrestrial and cable transmissions and to process them into a format suitable for reception by a conventional television set. Recently, it has been proposed to include a hard drive in a set top box to allow digital satellite and cable transmissions to be recorded and played back later. The received program information may be in MPEG-2 format. The set top box receives a stream of digital data from the satellite or cable link, parses it, and feeds it through a processor, so that the program data is recorded digitally in files in a local storage medium, e.g. a hard drive or Winchester disc. The program data can then be accessed from the hard drive, relayed through a conventional video decoder and fed to the television set.
It is likely that the capacity of suitable hard discs will increase to hundreds of hours so that a set top box may be used to store one or more whole days of programming content broadcast on a communication channel. This is in marked contrast to the conventional use of a videocassette recorder (VCR), which can only store a few hours of programming content on videotape. Here, a viewer decides which programs they would like to watch in advance of their transmission and records a selected number. With an increased capacity, a set top box may store a large number of programs, allowing a user to make viewing decisions after the recording has been made.
Furthermore, when a viewer watches television broadcasts as they are transmitted, it is possible for a content provider to promote their programs using trailers, potentially raising the viewer's interest in programs of which they were unaware. However, where a large number of programs have been stored, such as a full day's output from a television channel, it is more difficult to raise the viewer's interest in programs that have been inadvertently or unintentionally recorded.
Proposals have been made previously for sending trailers. U.S. Pat. No. 5,541,738 discloses sending trailers in advance to a program guide and downloading them to a video recorder so that the recorder can be primed in advance to record a program broadcast later. U.S. Pat. No. 5,945,987 discloses sending trailers from a video on demand system to customers. The user can browse trailers and jump between them in real time before choosing and downloading an associated program.